1. Field of the Invention
The invention relates generally to systems in which imagery is acquired primarily to determine or verify the identity of a person using a biometric recognition system, and more specifically to systems in which there is a need to detect the presence of a live, human eye in the imagery. The biometric used for recognition may be the iris, for example.
2. Description of Related Art
Like a fingerprint, an iris can be used to uniquely identify a person. A number of systems have been implemented for this purpose. For one example, U.S. Pat. No. 4,641,349, titled “Iris Recognition System,” issued to Flom et al. on Feb. 3, 1987, and U.S. Pat. No. 5,291,560, titled “Biometric Personal Identification Based on Iris Analysis,” issued to Daugman on Mar. 1, 1994, discloses a system for identifying a person based upon unique characteristics of the iris. A camera captures an image of the iris, the iris is segmented, and then the iris portion is normalized to compensate for pupil dilation. The normalized iris features are then compared with previously stored image information to determine whether the iris matches.
For another example, U.S. Pat. No. 5,572,596, titled “Automated, Non-Invasive Iris Recognition System and Method,” issued to Wildes et al. on Nov. 5, 1996, discloses an alternate method of performing iris recognition using normalized correlation as a match measure. Further advantages and methods are set forth in detail in this patent.
For another example, U.S. Pat. No. 6,247,813, titled “Iris Identification System and Method of Identifying a Person through Iris Recognition,” issued to Kim et al. on Jun. 19, 2001, discloses another system used for iris recognition, which implements a unique identification methods. The system divides a captured image of an iris into segments and applies a frequency transformation. Further details of this method are set forth in the patent.
For yet another example, U.S. Pat. No. 6,714,665, titled “Fully Automated Iris Recognition Systems Utilizing Wide and Narrow Fields of View,” issued to Hanna et al. on Mar. 30, 2004, discloses a system designed to automatically capture and identify a person's iris. This system uses a camera with a wide field of view to identify a person and a candidate iris. Once identified, a second camera with a narrow field of view is focused on the iris and an image captured for iris recognition. Further details of this method are set forth in the patent.
One problem faced by iris recognition systems involves the possibility of spoofing. Specifically, a life-sized, high-resolution photograph of a person may be presented to an iris recognition system. The iris recognition systems may capture an image of this photograph and generate a positive identification. This type of spoofing presents an obvious security concerns for the implementation of an iris recognition system. One method of addressing this problem has been to shine a light onto the eye, then increase or decrease the intensity of the light. A live, human eye will respond by dilating the pupil. This dilation is used to determine whether the iris presented for recognition is a live, human eye or merely a photograph—since the size of a pupil on a photograph obviously will not change in response to changes in the intensity of light. One disadvantage of this type of system involves the time required to obtain and process data as well as the irritation a person may feel in response to having a light of varying intensity shone into their eye.
U.S. Pat. No. 6,760,467, titled “Falsification Discrimination Method for Iris Recognition System,” issued to Min et al. on Jul. 6, 2004, attempts to address this problem. This system positions a pair of LED's on opposite sides of a camera. These LED's are individually lighted and images captured through a camera. These images are analyzed to determine whether light from the LED's was reflected back in a manner consistent with a human eye. Because a flat photograph will not reflect light back in the same manner, this system aims to deter this type of spoofing. One disadvantage of this system, involves the simplicity of the approach and the placement of the LED's. With two LED's positioned at a fixed, known location, the method can be defeated by appropriate placement of two small illuminators in an iris image. Also, while this system may operate more quickly than systems that dilate a pupil, it still requires time to capture at least two separate images: one when each of the two LED's are individually lit. Further, a third image needs to be captured if the system requires both LED's to be illuminated to capture imagery that is sufficiently illuminated for recognition.
The above identified patents are each incorporated herein by reference in their entirety as well as each of the patents and publications identified below.
As mentioned above, it is well known that imagery of the iris can be reliably matched to previously recorded iris imagery in order to perform reliable verification or recognition. For example, see Daugman J (2003) “The importance of being random: Statistical principles of iris recognition.” Pattern Recognition, vol. 36, no. 2, pp 279-291. However since the iris patterns are not easily recognizable to a human, it is impossible to demonstrate to a user who has been rejected from any iris recognition system the reason for the rejection. On the other hand, if a face image of the person whose iris has been used for recognition is acquired, it is easy to demonstrate the reason for rejection since face imagery can be easily interpreted by humans. Therefore, especially in unattended systems, there is a need for a highly secure method of associating an acquired face image to an acquired iris image, preferably (although not necessarily) with just one sensor in order to reduce cost and size of the solution.